PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 803 
Figured specimens.—117545a,b; measured specimen: 117545c. 
Horizon and locality—Rodman member of Nealmont formation in Pennsyl- 
vania: I mile northeast of Bellefonte, Bellefonte (15’) Quadrangle. 
Discussion.—This species is suggestive of S. monilifera from Iowa but is pro- 
portionally longer, has a more erect pedicle beak, less swollen pedicle valve, and 
shorter pedicle interarea. 
SOWERBYELLA sp. 3 
Plate 196, G, figures 45-50 
Shell small, wider than long, hinge equal to or wider than the midwidth de- 
pending on age; costellae well differentiated, 2 of the larger costellae occupying 
I mm. and as many as 5 costellae separating the larger ones at the front margin; 
posterior margin of both valves marked by prominent oblique wrinkles. Pedicle 
valve moderately convex and with the greatest convexity near the middle in 
lateral profile ; anterior profile broadly and moderately convex ; umbo and median 
region broadly swollen and merged with the flanks. Brachial valve with the 
maximum concavity in the umbonal region, rest of valve moderately concave ; 
posterolateral extremities flattened. 
Measurements in mm.—117546, length 6.9, brachial length 6.5, midwidth to.1, 
hinge width 11.2 ?, thickness 1.3, height 2.1. 
Figured specimen.—117546. 
Horizon and locality—Lower part of the dark shale under the Eureka quart- 
zite in Nevada: On the north-facing nose of hill 8167, Martins Ridge, Monitor 
Range, Roberts Mountains (1°) Quadrangle. 
Discussion —This is a small species with well-differentiated costellae which is 
less deep than Sowerbyella sp. 1. It is suggestive of S. silicica but is larger and 
does not have the small fold and sulcus of that species. It differs from S. vari- 
costellata in not having the pedicle valve subcarinate and the brachial valve dis- 
tinctly sulcate. 
SOWERBYELLA sp. 4 
Plate 196, B, figures 9-14 
Shell small, wider than long; hinge wide, cardinal extremities auriculate; 
2 large costellae occupying 1 mm. at the front margin and large costellae sepa- 
rated by a maximum of 5 fine costellae. Pedicle valve gently convex in lateral 
profile ; anterior profile narrowly rounded in the middle with the sides somewhat 
depressed and sloping steeply to the margins. Median region subcarinate; fold 
low; flanks gently inflated. Brachial valve not deeply concave, deepest along 
the median line in the form of a narrow sulcus extending from umbo to 
anterior margin. Sides gently convex to flattened. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness Height 
Ty dsY7 y ae ime P54. MN 6.1 5.7, 8.4 8.3 ? 123 1.9 
PIG SAGA eS cee toeec ats 5.1 4.9 6.9 8.0 1.4 2.0 
PI7ZSASD eset e ee Se as 5.3 5.1 Gin 8.2 2 1:7 
